Hey Gang,

Standard FE cast iron head with CJ valves.
Stroked 445 with roughly 9.5:1 compression
Block is bored 30 over.

Going with Cometic .027 compressed thickness gasket. It comes in 4 bore sizes.
4.080
4.165
4.250
4.400

Which bore size do you recommend.

 

Your block started life as a 390? 4.050 bore, now 4.080 bore. You should use one about 4.090. You may be able to use the 4.080 one if it's clear of the bore and chamfer and any part of the combustion chamber. Otherwise, the 4.165.

That seems to be too big to me. No other options?

 

My 390 had a pretty big valve-relief in the bore after my mechanic clearanced it for the larger CJ-size exhaust valve. Just sayin'

 

Good point, it has to be clear of that and not "hanging" out I the open.

 

Go with the 4.165, with a 4.080 bore the 4.080 head gasket would have to have prefect bore spacing and be in perfect alignment on the dowels, if not the wire ring sandwiched in the gasket may not seal properly and you'll blow a head gasket.


I'm a little confused about cutting a valve relief in the bore for a CJ valve, I've ran CJ valves in several 390 engines and never had to cut reliefs.

 

In my case, it wasn't so much a clearance issue, but a flow issue. My machinist didn't like how close the valve came to the bore.